<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    a = 100;
    function demo(e){
        function e(){};
        arguments[0] = 2;
        document.write(e);//2
        console.log(a);
        if(a){//a是undefined，不执行var b = 123;
            var b = 123;
            function c(){};
        }
        console.log("b " + b);
        var c;
        a = 10;
        var a;
        document.write(b);//undefined
        f = 123;
        document.write(c);//function c(){}
        document.write(a);//10
    }
    var a;
    demo(1);
</script>
</body>
</html>
